A user interface (UI) is a space where an interaction between a human (i.e. end user) and a machine (i.e. client) occurs. A UI is generally measured by its efficiency, user experience and ease of use by the client. One example of a UI is a web based UI, where data is transmitted from a server to a client through a network. This data appears to the client as a web page in a browser.
A web page allows rendering of information such as a client-server application, which is the most common web UI, due to its support of cross-platform compatibility. This cross-platform compatibility is achieved because any client who has a browser can view the web page, without installing any additional software on his device.